Metal honeycomb body of intertwined sheet-metal layers, and method for its production

ABSTRACT

A metal honeycomb body is disposed within a jacket member. At least partly structured sheet-metal layers are wrapped around one another and extend alternatingly back and forth in a curved, preferably involute, fashion between an outer annular region and an inner annular region of the honeycomb body. The sheet-metal layers form loops. At least three reversal lines are defined in the outer annular region, and the sheet-metal layers are intertwined about these reversal lines. A method for producing the honeycomb body includes the following steps: forming or winding a multi-layer hollow coil from at least one sheet-metal strip which has at least partial structuring; deforming the multi-layer hollow coil from the outside thereof towards the inside at at least three lines such that the at least one sheet-metal strip extends in loops between outer and inner reversal lines; and compacting the resulting deformed multi-layer structure about the inner reversal lines by rotationally intertwining the loops formed by the folded sheet-metal layers in a given direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to a honeycomb body, particularly a catalystcarrier body, which is formed of at least partly structured metal sheetsdefining a plurality of channels through which a fluid can flow.

2. Description of the Related Art

It is known from German published, non-prosecuted application 23 21 378to produce honeycomb bodies from a ribbon of sheet metal, by providingthe sheet-metal ribbon with fold lines, folding it, and inserting itinto a cylindrical case. The ribbon is disposed around a center, andboth the outer circumferential segments pointing toward the center ofthe ribbon and those pointing outward form circles. The sheet-metalribbon itself remains uncorrugated, so that overall, only a few flowchannels of large cross section are formed in the honeycomb body. Thesheet-metal is covered with catalyst material. A cylindrical void thatcannot be utilized for the catalytic conversion process remains in theinterior of the metal carrier.

From European application EP 245 737 (corresponding to U.S. Pat. Nos.4,832,998 and 4,923,109), it is known to produce honeycomb bodies from anumber of individual sheet-metal layers. Alternating corrugated andsmooth sheet-metal segments are layered into a stack. The stack is thenintertwined around two fixed points, producing a honeycomb body whosesheet-metal layers are arranged approximately in the shape of an S. Thisis the so-called S-form catalyst.

From German published, non-prosecuted application 33 41 868(corresponding to U.S. Pat. No. 4,647,435), it is known to produce ahoneycomb body from a sheet-metal strip folded on itself in a meanderingor zig-zag fashion. The strip is provided with prefabricated creaselines at the folding points.

The known prior art has numerous disadvantages. In German 23 21 378, forinstance, the catalytically active surface area is too small; especiallyfor use in motor vehicles, a considerably larger catalyst surface area,with simultaneously very compact outer dimensions, are desired. In EP245 737, the honeycomb body is produced from individual sheet-metalsegments. The handling of these segments is problematic, however,because the sheets are very thin and have a very smooth surface andhence can easily stick together. In production, particular care must betaken in this respect. While German 33 41 868 avoids a number of thesedisadvantages, the honeycomb body is very rigid, so that it does notalways withstand thermal strains. Moreover, the way in which the zig-zaglayers are folded on one another is very labor-intensive.

European application EP 0 245 736 discloses a honeycomb body in whichthe individual sheet-metal layers have an involute course in the outerregion. This leads to a very uniform structure and great durability inthe face of thermal strains. The international publication WO 90/03220(corresponding to U.S. Pat. Nos. 5,105,539; 5,135,794; and 5,139,844),from which the instantly disclosed invention starts out, also disclosesan especially favorable method for producing such honeycomb bodies.Three or more stacks of sheets, which are at least partly structured,are intertwined with one another.

The configurations have many advantages, particularly since the forcesdue to alternating thermal strains are uniformly distributed in thehoneycomb body. One of the disadvantages, as must be pointed out,however, is that many sheets have to be cut to a suitable length andthen stacked into stacks. The individual sheet-metal layers are also notlong enough that electric conductors of sufficient length for heatingthe honeycomb body or for representative measurement over the entirecross section can be integrated into a single such sheet.

International publication WO 91/14855 also discloses a honeycomb bodyhaving at least one integrated electric conductor. When the conductor islaid in a simple, straight course, it can have only a limited length.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a metalhoneycomb body of intertwined sheet-metal layers, and a method for itsproduction, which overcomes the herein-afore-mentioned disadvantages ofthe heretofore-known devices and methods of this general type and tofurnish a honeycomb body with a large catalytically usable surface area,which can be produced with only a few production steps from a smallnumber of metal sheets, and which is able to withstand alternatingthermal strains.

It is a further object of the present invention to provide a honeycombbody, particularly a catalyst carrier body in a catalytic converter forcleaning the exhaust gas of motor vehicle engines, which comprises onlya small number of metal sheets, is uniform in construction, and thestructure of which is also suitable for integrating at least one longelectrical conductor in at least one of the sheet-metal layers, or toform one of the sheet-metal layers itself as a long, insulatedelectrical conductor.

With the foregoing and other objects in view there is provided, inaccordance with the invention, a metal honeycomb body, comprising ajacket member defining an interior with a substantially annular innerregion and a substantially annular outer region, at least partlystructured sheet-metal layers disposed in the interior, the sheet-metallayers being wrapped around one another and extending alternatingly backand forth in a curved fashion between the outer annular region andthe-inner annular region, and the sheet-metal layers forming loops, andat least three reversal lines defined in the outer annular region, thesheet-metal layers being intertwined about the at least three reversallines.

In other words, the objects of the invention are attained with a metalhoneycomb body having sheet-metal layers, which are at least partlystructured, wrapped around one another, which extend alternatingly backand forth in curved, and in particular in approximately involute,fashion between an outer annular region in the vicinity of a jacketregion and an inner annular region in a center region and form loops,wherein the body in the outer annular region in the vicinity of itsjacket, and in the inner annular region in the vicinity of its center,has at least three reversal lines, around which the sheet-metal layersare intertwined.

In accordance with an added feature of the invention, the jacket memberdefines a longitudinal axis of the honeycomb body in a center thereof,the reversal lines extend substantially parallel to the longitudinalaxis, and the sheet-metal layers are curved in an approximately involutefashion.

In accordance with an additional feature of the invention, thesheet-metal layers are formed by one to five sheet-metal strips havingat least in part a corrugation-like structure, and the reversal linesextend through two or more mutually concentric circles.

In accordance with a further feature of the invention, the honeycombbody has a given cross-sectional shape, and the reversal lines aredistributed within the jacket irregularly in accordance with thecross-sectional shape of the honeycomb body. By simply distributing theinner reversal lines in a certain way, the resulting honeycomb shape maybe varied in a number of different ways.

In accordance with again added features of the invention, the loops aredisposed within the inner annular region and the sheet-metal layerssubstantially fill the inner annular region, or a void of a certainshape is retained on the inside of the honeycomb body, into which nosheet-metal loops extend. The interior void may or may not be supportedwith a rigid central structure, such as a pipe.

In accordance with again an additional feature of the invention, atleast some of the sheet-metal layers are formed of corrugated metalstrips having a longitudinal edge, the corrugated strip having acorrugation with troughs and peaks extending in a direction whichdeviates from a perpendicular to the longitudinal edge of the metalstrip by an angle of from 2° to 10°. When the corrugated structures arethus folded onto one another--with their longitudinal edges remainingparallel--the corrugation troughs and valleys intersect one another andform a mutual angle of twice the chosen corrugation angle.

In accordance with again a further feature of the invention, honeycombbody includes a layer with an integrated electrical conductor, theelectrical conductor being electrically insulated from adjacentsheet-metal layers, the electrical conductor being, for instance, a hotconductor for heating the honeycomb body or a measurement sensor.

In accordance with yet an added feature of the invention, the layers areformed of at least partly corrugated sheet metal strips and smoothsheet-metal strips each extending along a longitudinal axis, the layersbeing folded one on top another and defining apex points at the loops,the sheet-metal strips having lateral edges into which mutually opposedcut-outs are formed at the apex points such that a relatively narrowerweb is defined between the cut-outs and strip segments are definedbetween the apex points, adjacent ones of the strip segments beingrotated relative to one another by 180° about the longitudinal axis.

With the objects in view, there is further provided, in accordance withyet another feature of the invention, a honeycomb body, comprising astack of sheet-metal layers disposed in the form of an S, the stackbeing formed of a corrugated, smooth or corrugated and smoothsheet-metal strip folded in zig-zag fashion.

With the above-noted objects in view, there is also provided, inaccordance with the invention, a method for producing a metal honeycombbody of at least partly structured sheet-metal layers. The methodcomprises the steps of:

a) forming a multi-layer hollow coil with an inside and an outside fromat least one sheet-metal strip which has at least partial structuring;

b) defining an inner annular region and an outer annular region on theinside of the multi-layer coil;

c) deforming the multi-layer hollow coil from the outside thereoftowards the inside at at least three lines distributed about acircumference of the multi-layer hollow coil, and forming acorresponding number of inner reversal lines in the inner annular regionand outer reversal lines in the outer annular region, such that the atleast one sheet-metal strip extends in loops between the outer and innerreversal lines; and

d) compacting the resulting deformed multi-layer structure about theinner reversal lines by rotationally intertwining the loops in a givendirection.

As will also be described in detail in conjunction with the drawing,such a honeycomb body can easily be produced from a hollow coil byfolding it in a star shape and then wrapping the "points of the star"around one another. The hollow coil comprises structured metal sheetswound in a spiral around one another, which form a hollow cylinder whoseouter radius is R and whose inner radius is r. The cross-sectional areaof the hollow cylinder, i.e. the area about which the sheet-metal layersare distributed, is in fact π (R² -r²) and is approximately equivalentto the cross-sectional area of the honeycomb body to be produced laterfrom the hollow coil. In the simplest case, the hollow coil consists ofa single-flight spiral of one smooth and one corrugated metal sheet, butthe possibility also exists of producing a multi-flight spiral fromalternating smooth and corrugated sheets, for instance. Alternatinglayers of differently structured sheets are also possible, such assheets corrugated obliquely at an angle, many versions of which areknown from the prior art. By way of example, the hollow coil can beproduced easily by winding the sheet-metal layers onto a cylindricalcore.

Next, however, the hollow coil is not pressed flat and then intertwined,as known from the prior art, such as European application No. 332 891B1, but instead is pressed in from the outside inward at at least threepoints, forming a star shape. The "points" of the star may be wrapped inthe same direction around the center of the star, forming a desiredcross section filled closely with structured sheet-metal layers. Theindividual sheet-metal layers then have an approximately involutecourse, except that, unlike the prior art, the sheet-metal layers areself-contained so that no free ends emerge on the outside; instead, onlythe curved backs of sheets are located on the outside.

The number of reversal lines, which is the same for both directions ofcurvature, should preferably be at least 4 each on the inside and on theoutside. In certain applications, particularly when a honeycomb bodythat has a hollow inner annular region is to be produced, an even largernumber is in fact desirable. The difference between the outer and innerradii (R-r) of the hollow coil and the number of reversal lines, as wellas their initial distribution over the circumference of the hollow coil,determine the later shape of the cross section or in other words thesize of a hollow inner annular region.

In principle, the hollow coil can be built up in many ways; preferably,1 to 5 sheet-metal strips are used, which at least in part have acorrugation-like structure. "In part" means that either one sheet-metalstrip has this structure in some regions, or that some of thesheet-metal strips have this structure. For instance, it is possible toproduce a hollow coil from a single sheet-metal strip which is smoothover half its length, for instance, and corrugated on the other half andthen is folded together. A configuration with one smooth and onecorrugated sheet-metal strip or a plurality of such strips is alsopossible; all the structures and substructures of the sheets known fromthe prior art may be used. The hollow coil preferably has a total of 3to 7 layers, each of which is produced by winding up the 1 to 5sheet-metal strips.

The present invention is especially highly suitable for honeycomb bodiesin which at least one electric conductor that is electrically insulatedfrom the honeycomb body is to be integrated, the conductor beingembodied as a hot conductor and/or as a measuring sensor. To produce atemperature sensor that representatively measures over the cross sectionof the honey comb body, it is important incorporate a relatively longconductor. The same is true for a hot wire in electrically heatablehoneycomb bodies. Here, the present invention offers the advantage, overhoneycomb bodies that comprise a number of individual sheets, that along conductor, such as a wire, can be integrated into one of thesheet-metal layers without difficulty, preferably a corrugatedsheet-metal layer. As is known, an electrical conductor can thus bedisposed in a jacket conductor, for instance, and rolled in between twosheet-metal layers. Any other way of integrating an electrical conductorinto a sheet-metal layer is also possible, such as laying it into aslit, corrugated sheet-metal layer. Ducting the electric conductorthrough a window into a jacket tube that might optionally surround thehoneycomb body can be done, for instance, in accordance withinternational publication WO 93/05284, which teaching is herebyexpressly incorporated by reference.

In general, a honeycomb body according to the invention is surrounded bya jacket tube, and the outermost sheet-metal layer touches the tubealong lines of contact in the vicinity of the outer reversal lines. Tosecure the honeycomb body in the jacket tube, the outermost sheet-metallayer may be joined to the jacket by brazing, at least in subregions ofits contact lines with the jacket.

The sheet-metal layers are preferably also joined to one another bybrazing, at least in subregions. Such brazing connections are preferablymade at one or both end faces of the honeycomb. The end faces of thehoneycomb body are defined at the entry point of the fluid into the bodyand the exit point of the fluid out of the body.

In paraphrasing the claimed method, the production of the honeycomb bodyfrom sheet-metal layers follows these steps:

a) a hollow coil with a plurality of sheet layers, preferably 3 to 10sheet layers, is wound from 1 to 10, and preferably 3 to 5 sheet strips(3, 4), which are at least partly structured; the hollow coil is, infact, an annular ring and possibly a multi-layer annular ring;

b) the hollow coil, supported from inside, is deformed from the outsideinward at at least three lines, so that a corresponding number ofreversal lines are formed both in an outer annular region and in aninner annular region;

c) the resultant starlike structure is compacted by rotationalintertwining of the outer reversal lines, relative to the inner reversallines.

As will be seen in further detail from the description of the drawing,this production method is very rapid and simple and has only a fewindividual steps. Nevertheless, by a suitable selection of thedimensions of the hollow coil and of the number of reversal lines, whichmoreover need not be distributed uniformly over the circumference of thehollow coil, several different forms may be produced, analogously to therange of forms already known from the prior art. The reversal lines, asshown in the drawing, may also be located on a plurality of concentriccircles or distributed irregularly in the finished honeycomb body, inorder to produce special shapes.

For instance, the hollow coil may be deformed from the outside inward atat least four lines; to form non-round cross sections, the reversallines are circumferentially spaced apart at uneven intervals.

It is completely unproblematic in this production process to integrateat least one sheet-metal strip, which is formed of two sheet-metallayers in close contact with one another between which at least oneelectrical conductor is integrated in an electrically insulated manner.Without any change whatsoever in the production process, a very longelectrical conductor can in this way be distributed uniformly over thecircumference of the honeycomb body and can serve as a measurement probeor sensor or as a hot conductor.

As also known in the prior art from which the instantly disclosedinvention starts out, one of the substantial advantages of the presentinvention is that a honeycomb body with a hollow inner central regioncan be formed in a simple way. That configuration need not even besupported by a central tube.

The honeycomb body is preferably produced from a thin corrugated metalstrip--the material thickness is approximately 0.02 mm to 0.1 mm. Thecorrugated strip extends in alternation from a center to a jacket andfrom there back to the center. Each location of the corrugated stripthen comes to rest on the adjacent layer of the strip, producing aspiral or involute structure for the metal carrier, with a plurality ofaxially extending channels. The radially inwardly pointing loops of themetal strip rest with their apices inside the center, which theyactually fill virtually completely. The distribution of the loops in thecenter need not be symmetrical. The radially outwardly pointing loopsare wrapped around the radially inner loops and hence about the center,producing the spiral form already described. The outer regions of theloops are joined to a surrounding jacket housing by fastening techniquesor in a form-locking fashion.

Because the corrugated sheet rests on itself in a looped fashion, caremust be taken so that the corrugations of two corrugated sheet layersresting on one another will not nestle into one another. Rather,channels of a defined cross section which allow a fluid flow need to bemaintained. This problem is solded by way of a special corrugation shapein the corrugated strip, for instance in accordance with Germanpublished, non-prosecuted application 33 47 086. However, thecorrugation may also be impressed obliquely with respect to thelongitudinal course of the strip. It has proved especially advantageousfor the corrugation to deviate by about two to ten degrees from beingperpendicular to the edge of the corrugated strip. When the corrugatedstrip is folded onto itself in looped or zig-zag form, the corrugationsof the strip thus intersect one another (by twice the chosen angle),thereby preventing the corrugated strips from sliding into one another.

Another option for preventing two corrugated strips from falling intoone another is to insert smooth divider strips. Preferably thecorrugated strip is disposed between two smooth strips. If thethus-arranged smooth and corrugated strips contact one another in loopedor zig-zag fashion, the smooth strip on the inside in each case comes torest on itself, so that the corrugated strip is always supported on thisdouble smooth strip layer, and the smooth strip can be selected assuitably thin, for instance being 0.02 mm thick.

In a further preferred embodiment, a plurality of corrugated and smoothstrips are incorporated into the honeycomb body. Then each corrugatedstrip is disposed between two smooth strips, so that a smooth stripalways alternates with a corrugated strip. The outer layer should be asmooth strip, because otherwise in a looped or zig-zagged arrangementtwo sides of a corrugated strip would come to rest on one another. As aresult of this arrangement with multiple smooth and corrugated stripsone on top of the other, it is possible to fill even relatively largehoneycomb body cross sections, without having to increase the number ofloops or wrappings around the center to a great extent.

Another option for separating the looped corrugated sheets is to slideindividual smooth strip segments in between the corrugated strip layers.Then the sheet-metal segments are inserted between the corrugated striplayers both from the center and from the edge, so that the smooth stripsegments are in approximately a star-shaped arrangement. The smoothstrip segments pointing outward are wrapped with the radially outer looparound the center and are joined to the jacket by fastening techniques,such as brazing, or in a form-locking fashion.

To prevent two layers of corrugated strip material from sliding in oneanother, one layer of smooth strip may for instance be inserted betweenthem. To that end, one smooth strip and one corrugated strip are placedon one another. At the apex points of the loop, both strips aresimultaneously cut out or stamped out from both edges, so that only anarrow web remains in the middle of the strip. The smooth and corrugatedstrip segments between two such narrow webs are the twisted about thelongitudinal axis by 180° relative to the adjacent strip segment. Whenthe strips are then laid on one another in looped or zig-zag form, inwhich the segments correspond to the width of the zig-zag stack, asmooth layer and a corrugated layer always come to rest on one another.

As described above, the honeycomb body is produced by winding up atleast one corrugated metal strip to make a single-layered ormulti-layered hollow coil. The corrugated strip is placed over windingmandrels, which at the same time are disposed on a circle having theinside diameter D1. The number of winding layers is determined by thedesired thickness of the loops subsequently made, which in turn dependson the required diameter of the honeycomb body. The number of windingmandrels is as a rule selected such that it matches the number of loopsrequired to produce the metal carrier, so that once the loops have beenintertwined around the center, the corrugated strip will precisely fillthe interior of the honeycomb body.

In the second processing step, the corrugated strip is pulled in betweenthe winding mandrels toward the center of the honeycomb body. To thatend, draw-in mandrels are brought from the outside against the circlemade by the corrugated strip, and the corrugated strip is also drawninto the center by these draw-in mandrels, in the course of which thewinding mandrels yield resiliently, so that the corrugated strip willnot be overstretched. After the drawing in, the corrugated strip, whichbefore was arranged in a circle, is now deformed into a rosette shape,and the winding mandrels are now disposed on a reduced circular diameterD2.

In the next production step, the winding mandrels are removed. Theradially outer loops are wrapped around the radially inner loops. In theprocess, the corrugated strips are pressed against the neighboringcorrugated strip layers, producing a spiral structure with the outsidediameter D3 for the honeycomb body. During the intertwining process, thedrawn-in mandrels serve as retainers for the loops, so that these loopsare fixed in the center region. Finally, the honeycomb body produced inthis way is inserted into a jacket and fastened thereto by fasteningtechniques or in a form-locking manner.

This production method may be modified so that during the winding of thecorrugated strip onto the winding mandrels, two smooth sheets areadditionally delivered, so that the corrugated strip runs between thetwo smooth strips. This is necessary whenever the embossing of thecorrugated strip does not prevent two corrugated strip layers resting onone another from slipping into one another, as can happen with a simplesinusoidal corrugation, for instance.

Given the requirements of modern automotive engineering, honeycombbodies that deviate from the circular form are often used. Theelliptical or stadium-shaped metal carriers that are often used areproduced by embodying the center of the metal carriers not in point orcircular form but rather that it assumes virtually a linear form.Elliptical metal carriers can accordingly be produced so that theradially inner loops are pulled into a straight line, whichapproximately connects the two foci of the ellipse. Other forms ofhoneycomb bodies can be produced easily in this way, and for differentgeometrical versions the center is adapted appropriately, for examplebeing curved.

Honeycomb bodies of several special geometrical shapes cannot beproduced in the foregoing manner. An example therefor being bone-shapedhoneycomb bodies. To produce those shapes, it is proposed that thelengths of the loops not be made uniform but rather varied. This makesit very simple to change the external form of the honeycomb body.

A further version or honeycomb bodies is to arrange stacked corrugatedand smooth sheets in an S-shaped configuration in a jacket. This kind ofembodiment can also be achieved with a single smooth and/or corrugatedstrip. A stack of metal strips placed in zig-zag fashion on one anotheris made and then intertwined about two fixed points, producing theaforementioned S-shaped configuration.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a metal honeycomb body of intertwined sheet-metal layers, and methodfor its production, it is nevertheless not intended to be limited to thedetails shown, since various modifications and structural changes may bemade therein without departing from the spirit of the invention andwithin the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a first embodiment of a honeycombbody according to the invention;

FIG. 2 is a schematic cross-sectional view of a hollow coil from whichthe honeycomb body of FIG. 1 may be formed;

FIG. 3 is a partial view of the hollow coil of FIG. 2, partiallydeformed into a star shape;

FIG. 4 is a view similar to that of FIG. 2 with a distribution ofreversal lines for the formation of a second, i.e. oval, embodiment ofthe honeycomb body;

FIG. 5 is a schematic view of a further exemplary embodiment withreversal lines distributed over a plurality of concentric circles;

FIG. 6 is a cross-sectional view of an embodiment with an irregulardistribution of the reversal lines;

FIG. 7 is a similar partial view of a honeycomb body with a hollow innercentral region;

FIG. 8 is a similar view of a honeycomb body with an irregular crosssectional shape;

FIG. 9 is a partial, perspective view of a corrugated sheet-metal layerwith an integrated electrical conductor for integration in a honeycombbody according to the invention;

FIG. 10 is a schematic cross-sectional view of a round honeycomb body;

FIG. 11 is a similar view of an elliptical honeycomb body;

FIG. 12 is a schematic view of a honeycomb body prior to theintertwining, with loops of different lengths;

FIG. 13 is a similar view of the honeycomb body after the intertwining,with loops of different lengths;

FIG. 14 is a schematic view of a corrugated strip with obliquecorrugation and a corrugation of an adjacent layer strip superimposedthereon;

FIG. 15 is a cross-sectional view of a folded stack;

FIG. 16 is a similar view of the stack intertwined about two fixedpoints;

FIG. 17 a diagrammatic view of the honeycomb body with twistedsheet-metal strip segments;

FIG. 18 is a partial view of a detail of a sheet-metal strip segmentwith a web;

FIG. 19A is a diagrammatic side-elevational view of a corrugated stripwound into a circle,

FIG. 19B is a similar view of the corrugated strip drawn into a rosette;

FIG. 19C is a similar view of the honeycomb body twisted into a spiral;

FIG. 20 is a diagrammatic view of smooth and corrugated strips wound upin a circle; and

FIG. 21 is a similar view of the corrugated strip disposed in a rosetteshape, smooth strip segments thrust in between.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings in detail, and first, particularly, toFIG. 1 thereof, there is seen a schematic cross-sectional view showingthe construction of a honeycomb body of the invention, using a roundcross section as an example. The honeycomb body comprises alternatingsmooth sheet-metal layers 3 and corrugated sheet-metal layers 4 disposedin a jacket tube 1. The illustrated corrugations are simple sinusoidalcorrugations with rounded troughs and peaks. It is understood, however,that any number of corrugation types may be employed in conjunction withthe invention. Three or more inner reversal or inversion lines 2a, 2b,2c, . . . are located within an inner annular region 5, and an equalnumber of outer reversal lines 7a, 7b, 7c, . . . are located in an outerannular region defined between a dashed circle 6 and the jacket 1. Thesheet-metal layers 3, 4 wind around these reversal lines, each layeralternating in its direction of curvature, and extend in a curve betweeneach two reversal lines, preferably in an approximately involutefashion. The lines of contact of the outermost sheet layer with thejacket tube 1 may, at least in partial regions, be joined to the jackettube by brazing. To avoid having sheet layers of the same structure reston one another, additional intermediate layers 10 may be provided, whichare laid in or inserted during an intervening step during thedeformation. It is noted that the cross-sectional view of most of thefigures may also be denoted end faces of the honeycomb bodies. In apreferred embodiment, the sheet-metal layers 3 and 4 are brazed to oneanother, at least in subregions of their mutual lines of contact, in thevicinity of the end faces.

FIG. 2 shows a schematic cross section of a hollow coil from which ahoneycomb body of the invention can be produced. In this exemplaryembodiment, the hollow coil comprises one smooth sheet 3 and onecorrugated sheet 4, which are wound in alternation in a spiral to make ahollow cylinder. This hollow cylinder is defined by five layers A-E andhas an outer radius R and an inner radius r, as measured from a centerpoint which lies on a longitudinal axis of the honeycomb body. Bypressing the hollow coil inwardly at the reversal lines 2a, 2b, 2c, 2d,the coil can be deformed to make a star-shaped structure. Under somecircumstances, the hollow coil might need to be supported from theinside at the reversal lines 7a, 7b, 7c, 7d, in order to achieve uniformdeformation. As a result of this deformation, the reversal lines 2a, 2b,2c, 2d come to be located within the inner annular region 5, while thereversal lines 7a, 7b, 7c, 7d initially form the "points" of a star. Anintermediate state along the way to this form is shown in a schematicdetail in FIG. 3. The arrows 8 represent the direction of motion inwardof the reversal lines 2a, 2b, 2c, 2d. If the "points" of the star arethen compacted, as indicated by arrows 9, by rotary twisting in the samedirection of the outer reversal lines 7a, 7b, 7c, 7d relative to theinner reversal lines 2a, 2b, 2c, 2d to make a tight body, then thedesired form of a honeycomb body is obtained.

FIG. 4 shows the initial disposition of the reversal lines 7a, 7b, 7c,7d and 2a, 2b, 2c, 2d for forming an oval honeycomb body. The reversalpoints 7a, 7b, 7c, 7d are not distributed uniformly over the insidecircumference of the hollow coil but instead are located at the cornersof a rectangle (rather than a square as in FIG. 2), so that with thestar-shaped deformation and later intertwining, an oval cross section isformed.

FIG. 5 shows an exemplary embodiment that can be preferably employedwhenever a larger number of connection points with the jacket 1 aredesired in the outer region and whenever a steeper angle of contact ofthe outer sheet layer is desired. By means of additional reversal points11a, 11b, 11c and 12a, 12b, . . . , the desired structure in the outerregion can likewise be formed from a hollow coil.

FIG. 6 schematically shows how an overly large internal void can beavoided, if that should be undesirable, when there is a relatively largenumber of outer reversal lines 13a, 13b, 13c, . . . and inner reversallines 14a, 14b, 14c, . . . and 15a, 15b, 15c . . . . To that end, someof the inner reversal lines 14a, 14b, 14c are located on a circle havinga smaller radius than that of the other inner reversal lines 15a, 15b,15c.

FIG. 7, by contrast, shows how a hollow inner central region, as definedby a tube 17, is formed. All of the inner reversal lines 16a, 16b, 16c,. . . are located on a concentric circle within the interior of theinner annular region 5.

FIG. 8 schematically shows an example of how irregular cross sectionscan be filled according to the invention. Here the inner reversal lines18a, 18b, 18c, 18d are irregularly located in the interior, and as aresult a correspondingly irregular cross section can be filled up in theintertwining process.

FIG. 9 shows how an electrical conductor 43, insulated and separatedfrom the metal sheets 3 and 4 by an insulation 45, can be disposedwithin one sheet layer. The layer is comprised of two individual sheets3 and 4. The sheets 3 and 4 have a bulge 46 on one or both sides, andthe other electrical conductor 43, electrical lead, probe, heater or thelike, is laid in this bulge. The individual sheets may be joined attheir face ends by a brazed connection 44.

Virtually nothing in the described production process for honeycombbodies is changed if instead of a single corrugated layer, a doublelayer with an integrated electric conductor as in FIG. 9 is used.

FIG. 10 schematically shows another embodiment of a circular honeycombbody configuration. Here the sheet metal layers 3 and 4, laid on oneanother in looped form, are disposed in an inner annular region 5 thatis disposed coaxially around the center 11 of the honeycomb body. Thesheets are intertwined about the center 11. In the process, the radiallyinner loops 21 fill the center 11 completely. The radially outer loops22, with their outsides, touch the enveloping jacket 1, to which theyare joined by metal fastening techniques (e.g. brazing) or in aform-locking manner. It is noted, in this context, that a form-lockingconnection is one which connects two elements together due to the shapeof the elements themselves, as opposed to a force-locking connection,which locks the elements together by force external to the elements. Thestructure of the honeycomb body is nearly spiral, and the spiralsoriginate approximately at the circular center 11. The spacing of thespirals from one another is substantially constant, because the spacingis defined by the amplitude of the sheet layers 3 and 4.

In FIG. 11, an elliptical honeycomb body is shown. Here the sheet layers3 and 4 are laid on one another in looped fashion and drawn with theradially inner loops 21 to make a striplike center 11, which is disposedin the middle of the honeycomb body, approximately surrounding astraight line 11' that connects the foci of the ellipse. The inner loops21 completely fill the center 11. The radially outer loops 22 areintertwined around the center line 11, and the individual layers of thesheets 3 and 4 come to rest on one another. Once again, the structure ofthe honeycomb body is spiral. The number of loops 21 and 22 depends onthe size of the area of the honeycomb body to be filled. In thisexample, 23 inner loops 21 are folded about draw-in mandrels 31 andpulled towards the center 11. The number of inner loops 21 or drawn-inmandrels 31 may be increased or decreased arbitrarily. The outer loops22 rest with the corrugations of the sheet layers 3 and 4 on thesurrounding jacket 1 and are joined to it by fastening techniques or ina form-locking way.

FIG. 12 shows a honeycomb body with loops of different lengths prior tothe intertwining. Here the sheet layers 3 and 4, extending over thewinding mandrels 32, have been drawn by the draw-in mandrels 31 withdifferent spacings, resulting in a variable loop length. The draw-inmandrels 31 are drawn toward the striplike center 11, and in thisexample the draw-in mandrels 31 have not yet reached the center 11.After the winding mandrels 32 are removed, the outer loops 22 are thenwrapped around the center 11 in the wrapping direction U.

FIG. 13 shows a "bone-shaped" honeycomb body, which is produced from thesheet layers 3 and 4 arranged in loops, as shown in FIG. 12. Here thecenter 11 is striplike; it encloses the straight line 11' that connectsthe foci of the two knob-shaped ends. The honeycomb body is insertedinto a jacket 1 and joined to it by either fastening techniques or bymeans of a form-lock.

FIG. 14 shows a corrugated strip 4 with oblique corrugation, Here thecorrugations 41 deviate from a line 40, which is perpendicular to edges39 of the strip 4, by an angle α. By folding over the corrugated strip 4at the apices of the loops 21 and 22, two layers of the corrugated strip4 thus come to rest on one another, with the corrugation 41 of the toplayer being oriented in the opposite direction from the corrugated striplayer beneath it. In that way, that the corrugations 41 of the top layerintersect the corrugations 41' of the corrugated strip layer beneath itat an acute angle (2α).

FIG. 15 shows an exemplary stack 50 with corrugated strip layers 4folded in a zig-zag fashion on one another. The stack is retainedbetween two fixed points 51. The ends of the stack 50 are wrapped in thewrapping direction around the fixed points 51, producing a honeycombbody whose layers are arranged approximately in an S.

FIG. 16 shows one such honeycomb body, with the wrapping of FIG. 15continued to a finished configuration.

Referring now to FIGS. 17 and 18, of which the former schematicallyshows an apparatus for producing a honeycomb body, one corrugated strip4 and one smooth strip 3 are delivered to the apparatus. A stampingdevice 60 stamps striplike parts out of the strips 3 and 4 from theedges 39 inward. Only a narrow web 65 (FIG. 18) in the longitudinal axisof the strips 3 and 4 remains. In the further course of the apparatus,strip segments 61' (defined between two stamped-out, narrow webs 65) arerotated by 180° about the longitudinal axis relative to the stripsegments 61, in the course of which the webs 65 are wound up in aspiral. In a subsequent folder apparatus, the strip segments 61 and 61',twisted counter to one another, are stacked up. The webs 65 are locatedat the apex points 66 of the loops. Accordingly, a stack is formed fromalternating smooth and corrugated sheet metal layers.

FIGS. 19a-19c illustrate the production of a further embodiment of thehoneycomb body. The corrugated strip 4 is delivered to the windingapparatus, which includes the winding mandrels 32. The corrugated strip4 is now wound up to make a hollow coil. The inside diameter D1 of thehollow coil is defined by the location of the winding mandrels 32. Inthe next production step, draw-in mandrels 31 are placed against thehollow coil and thrust between the winding mandrels 32 toward the center11 of the honeycomb body. By the drawing in of circular sectors 20, thehollow coil is deformed into a rosette shape. The winding mandrels 32are thrust towards the center 11, and as a result the outside diameterD2 of the rosette is smaller than the inside diameter D1 of the hollowcoil. The winding mandrels 32 located in the radially outer loops 22 arethen removed, while the draw-in mandrels 31 in the radially inner loops21 remain and fix the inner loops 21 in the center 11 during the ensuingintertwining process. After the intertwining, the drawn-in mandrels 31are also removed from the inner loops 21, so that finally a honeycombbody results formed from only the corrugated strip 4. The corrugatedstrip 4 is spirally arranged in the honeycomb body. The outside diameterD3 of the honeycomb body is smaller than the outside diameter of D2 ofthe rosette shape.

FIG. 20 shows the production of yet a further embodiment of thehoneycomb body. The single corrugated strip 4 and two smooth strips 3are simultaneously wound up to make one hollow coil. The corrugatedstrip 4 is located between two smooth strips 3, so that both the insidesand the outside of the hollow coil are formed by the smooth strip. Theproduction steps proceed analogously to those described in conjunctionwith FIGS. 19b and 19c.

FIG. 21 shows a corrugated strip 4 that has been drawn in to make arosette shape. Smooth sheet segments 70 are introduced into theinterstices between the corrugated strips 4. The sheet segments 70extend on the one hand toward the center 11 to the winding mandrels 32and on the other extend outward from the draw-in mandrels 31. As aresult, the individual layers of the corrugated strip 4 are eachseparated by one smooth sheet segment 70. After the winding mandrels 32have been removed, the outer loops 22 are wrapped around the center 11in the wrapping direction U. In this foregoing embodiment it is alsopossible to interchange the corrugated and smooth sheets, i.e. the strip4 is smooth and the inserted strips 70 are corrugated.

The present invention is especially suitable for producing metalcatalyst carrier bodies for motor vehicles in large-scale massproduction; the honeycomb bodies thus produced, because of theirsymmetrical design and the approximately involutely-extending layers,are especially resistant to alternating thermal strains and severemechanical strains.

We claim:
 1. A metal honeycomb body, comprising a jacket member definingan interior with a substantially annular inner region and asubstantially annular outer region, at least partly structuredsheet-metal layers disposed in said interior, said sheet-metal layersbeing wrapped around one another and extending alternatingly back andforth in a curved fashion between said outer annular region and saidinner annular region, and said sheet-metal layers forming loops, and atleast three reversal lines defined in said outer annular region, saidsheet-metal layers being intertwined about said at least three reversallines.
 2. The honeycomb body according to claim 1, wherein said jacketmember defines a longitudinal axis in a center thereof, said reversallines extend substantially parallel to said longitudinal axis, and saidsheet-metal layers are curved in an approximately involute fashion. 3.The honeycomb body according to claim 1, including at least threereversal lines defined in said inner annular region.
 4. The honeycombbody according to claim 3, wherein said at least three reversal lines insaid inner and said outer annular regions are at least four reversallines in said inner and outer annular regions.
 5. The honeycomb bodyaccording to claim 3, wherein said reversal lines extend through two ormore mutually concentric circles.
 6. The honeycomb body according toclaim 3, wherein the honeycomb body has a given cross-sectional shape,and said reversal lines are distributed within said jacket irregularlyin accordance with the cross-sectional shape of the honeycomb body. 7.The honeycomb body according to claim 1, wherein an empty hollow centralregion is defined inside said inner annular region.
 8. The honeycombbody according to claim 1, wherein said sheet-metal layers are formed byone to five sheet-metal strips having at least in part a corrugatedstructure.
 9. The honeycomb body of one according to claim 1, whereinthe honeycomb body has a given cross-sectional shape, and said reversallines are distributed within said jacket irregularly in accordance withthe cross-sectional shape of the honeycomb body.
 10. The honeycomb bodyaccording to claim 1, wherein said jacket member is a jacket tube, anoutermost sheet-metal layer being in contact with said jacket tube anddefining lines of contact, said outermost sheet-metal layer being joinedto said jacket tube by brazing, at least in subregions of said lines ofcontact.
 11. The honeycomb body according to claim 1, wherein saidsheet-metal layers define lines of mutual contact, said sheet-metallayers being brazed to one another at least in subregions of said linesof mutual contact.
 12. The honeycomb body according to claim 1,including two end faces between which said sheet-metal layers extend,said sheet-metal layers being brazed to one another in a region of saidtwo end faces.
 13. The honeycomb body according to claim 1, wherein someof said loops are disposed within said inner annular region and saidsheet-metal layers substantially fill-said inner annular region.
 14. Thehoneycomb body according to claim 1, wherein at least some of saidsheet-metal layers are formed of corrugated metal strips having alongitudinal edge, said corrugated strip having a corrugation withthroughs and peaks extending in a direction which deviates from aperpendicular to said longitudinal edge of said metal strip by an angleof from 2° to 10°.
 15. The honeycomb body according to claim 1,including smooth sheet-metal strips inserted between adjacent corrugatedsheet-metal strips for avoiding double layers in the honeycomb body. 16.The honeycomb body according to claim 1, including corrugatedsheet-metal strips inserted between adjacent smooth sheet-metal stripsfor avoiding double layers in the honeycomb body.
 17. The honeycomb bodyaccording to claim 1, including a layer with an integrated electricalconductor, said electrical conductor being electrically insulated fromadjacent sheet-metal layers, said electrical conductor being at leastone of a hot conductor and a measurement sensor.
 18. The honeycomb bodyaccording to claim 17, wherein said layer with said integratedelectrical conductor is a corrugated sheet layer including twosheet-metal strips, said electrical conductor being disposed betweensaid strips.
 19. The honeycomb body according to claim 18, wherein saidelectrical conductor is rolled in between said strips.
 20. The honeycombbody according to claim 1, wherein said sheet-metal layers are formed bya corrugated metal strip and two smooth metal strips, said corrugatedmetal strip being disposed between said two smooth metal strips.
 21. Thehoneycomb body according to claim 1, wherein said sheet-metal layers areformed by a plurality of corrugated metal strips and smooth metalstrips, said corrugated metal strips being disposed between said smoothmetal strips.
 22. The honeycomb body according to claim 1, wherein atleast some of said layers are formed of corrugated sheet-metal strips,and including individual sheet-metal segments thrust in between saidlayers of said corrugated sheet-metal strips.
 23. The honeycomb bodyaccording to claim 1, wherein said layers are formed of at least partlycorrugated sheet metal strips and smooth sheet-metal strips eachextending along a longitudinal axis, said layers being folded one on topanother and defining apex points at said loops, said sheet-metal stripshaving lateral edges into which mutually opposed cut-outs are formed atsaid apex points such that a relatively narrower web is defined betweensaid cut-outs and strip segments are defined between said apex points,adjacent ones of said strip segments being rotated relative to oneanother by 180° about the longitudinal axis.